The invention concerns a throughput measurement device for the determination of the crop throughput in an agricultural harvesting machine, in particular a forage harvester, where the harvesting machine is provided with at least one pair of pre-compression rolls that guide the crop and whose spacing varies on the basis of the current crop throughput between a minimum limit position and a maximum limit position. The throughput measurement device contains a spacing measurement arrangement that makes available signals corresponding to the spacing between the pre-compression rolls, a speed sensor, that makes available signals corresponding to the speed of the crop and a control unit that utilizes the spacing signals and the speed signals for the determination of actual mass throughput values. Furthermore the invention concerns a harvesting machine with a throughput measurement device and process for the measurement of throughput.
In the treatise by G. Ihle and W. Dornitz, xe2x80x9cInvestigations into the Mechanical Measurement of the Throughput on Self-propelled Forage Harvestersxe2x80x9d, Agrartechinik, 27.Jg. issue 6, 5. 265 (1977) describes a continuous throughput measurement process for a forage harvester. In the forage harvester, the crop is conducted from a take-up arrangement over a transfer roll and a forward belt to compression rolls and smooth rolls (that are characterized in the following also as pre-compression rolls), which compress the crop to a mat and provide a speed corresponding to the currently effective chopper length for the mat. In a chopper drum, the crop mat is cut into individual lengths which are ejected through a discharge pipe to a transport vehicle. The height of the crop mat is detected by device and is used for the calculation of the throughput, in which the pre-set intake speed is considered a constant. On the basis of the process shown, the variation of the throughput with time can be recorded. However, it does not deliver any throughput signals that could be stored electrically and would be available for further control processes.
DE-A-195 24 752 discloses an arrangement and a process for the measurement of the throughput on a forage harvester with a throughput measurement device. Here the vertical movement of a pre-compression roll is transmitted over a lever linkage to the axis of rotation of a potentiometer which delivers lift signals corresponding to the lift path. An inductive sensor generates a signal value derived from the rotational speed of a pre-compression roll, which represents the throughput speed of the flow of the crop flowing through the machine. The signal values are continuously calculated in a microprocessor into an absolute mass flow measurement value. In addition, signals of a torque measurement at the chopper drum and a slip measurement of the drive belt can be detected and used as correction values in regions of defined limit values in which a pre-compression roll approaches the upper or lower stops. It has, however, been found that these corrections in the regions of the upper and lower stops are highly prone to errors and require a large calibration effort. Furthermore the linkage realignment of the vertical movement of a pre-compression roll over a lever linkage to the axis of rotation of a potentiometer described in DE-A-195 24 752 delivers a relatively low resolution of the measured values since the potentiometer disclosed covers a relatively small range of angles of rotation.
The problem underlying the invention is seen as that of defining a throughput measurement device, a harvesting machine with a throughput measurement device and a process for determining the crop throughput of the aforementioned type, through which at least some of the aforementioned problems are overcome. In particular, the throughput measurement device should permit a reliable and precise determination of the mass flow of crop with the employment of relatively few sensors. In the application of the measurement process a consideration of dynamic machine data should not be required.
According to the present invention, there is provided a throughput measurement device for the determination of the mass flow of the crop through an agricultural harvesting machine, in particular a forage harvester, that is provided with a pair of pre-compression rolls that guide and compress the crop, whose spacing varies on the basis of the current crop throughput between a minimum limit position and a maximum limit position.
A broad object of the invention is to provide a very reliable crop throughput measuring arrangement that uses few, cost effective sensors and components in an unobtrusive design, with the capability of high resolution even in the region of maximum deflection of the movable pre-compression roll without necessitating any dynamic machine data to be incorporated into the evaluation.
A more specific object of the invention is to provide a throughput measurement device containing a spacing measurement arrangement, which detects the spacing between the pre-compression rolls and makes available corresponding spacing signals and a speed sensor that detects the speed of flow of the crop in particular in the region of a pre-compression roll, and makes available corresponding speed signals, the measurement device further including a control unit which calculates, from the distance signals and the speed signals, actual mass throughput values.
Another object of the invention is to provide a throughput measurement device, as set forth in the immediately preceding object, but which further includes at least one force transducer that is arranged and is effective only in the region of the maximum limit position of the movable pre-compression roll, to produce signals corresponding to the pressures on the stop, with the control unit making use of these force transducer signals into the determination of the actual mass throughput values.
These and other objects will become apparent from a reading of the ensuing description together with the appended drawings.